1. Field of the Invention
The invention relates to turbine engine blade removal apparatus and methods for removing turbine or compressor section blades from turbine engine rotors. More particularly, the invention relates to turbine engine blade removal apparatus and methods that drive a stuck turbine or compressor blade root out of its corresponding rotor disc slot, minimizing risk of inadvertent damage to the blade root, the rotor disc slot or rotor discs. Exemplary embodiments of the methods and apparatus of the invention are utilized for non-destructive removal of gas turbine engine compressor section rotor blades that are stuck in their rotor slots, with the understanding that they are also useful for removal of turbine section blades.
2. Description of the Prior Art
Turbine or compressor blades (hereafter referred to generally as “turbine blades” or “blades”) are generally coupled to gas or steam turbine engines by elongated tapered male blade roots that are engaged in corresponding mating rotor disc female slots. The blade roots are inserted radially between rotor discs, aligned concentrically with the mating rotor slot and inserted in a generally axial direction that is generally parallel to the rotor shaft centerline. The blade root/rotor slot inserted axial positions are locked in place with blade lock pins that are inserted sequentially between each successive blade during rotor assembly. During turbine engine operation the mating turbine blade roots and rotor slots sliding interfaces as well as the blade lock pins become contaminated with rust and debris, effectively corroding them together as a unitized structure. The stuck blade needs to be removed by application of external force to separate the blade root from its rotor disc slot.
During turbine service repair, the turbine blades were separated from the rotor for repair and replacement. In the past, a corroded blade/slot/pin interface was separated manually by use of heavy sledge hammers or pneumatic hammers hammering an angularly offset drift punch abutted against the blade root within the peripheral boundaries established by the rotor slot. It was difficult to align and hold a drift punch in offset alignment with the blade root while hammering the drift punch. Manual alignment of the drift punch also risked inadvertent punch or hammer slippage that might inadvertently strike and damage any of the targeted or surrounding rotor discs, the targeted rotor disc slot and/or the blade root. Other manual turbine blade extraction methods have included destruction of the blade/blade root/pin interface by known grinding or milling metal working processes, but such methods destroyed the blade and risked damage to the rotor disc slot.
Powered blade removal tools have been utilized to push stuck blades out of their mating rotor slot. In U.S. Patent Publication No. 2001/0179645 a housing is inserted radially over a turbine, circumscribing the blade and both the corresponding proximal outer circumferential and axial faces of the rotor disc. The tool supports a pivoting cam mechanism and a cam-pivoting impact wrench between the subject turbine disc row and an adjoining opposed row. The impact wrench pivots the cam tip into contact with an abutting axial face of the blade root, driving the stuck root out of the rotor slot. In U.S. Pat. No. 4,445,730 a housing supporting a hydraulically-driven pivoting rocker arm and plunger is interposed between the subject turbine disc row and an adjoining opposed row. The housing is clamped over the subject rotor disc outer circumferential and axial faces. The hydraulic cylinder pushes down on a drive end of the pivoting rocker arm. A driven end of the rocker arm pushes the plunger into contact with an abutting axial face of the blade root, driving the stuck root out of the rotor slot. Both powered blade removal tools are relatively heavy and cumbersome for service technicians to position on the rotor. Both powered tools are more costly to construct and operate than manually operated stuck blade removal tools.